THIS is a very comprehensive treatise by Dr. Pictet, a former treatise by whom on a cognate subject was reviewed in NATURE in 1905 (vol. lxxii., p. 632). It begins with a résumé of previous researches by various authors, classified under several heads, and proceeds to describe the author's own researches and the conclusions he draws from them. Many of the details are highly interesting, and his observations upon them are of much weight.
Recherches Experimentales sur les Mecanismes du Melanisme et l'Albinisme chez les Lepidopteres. By Dr. Arnold Pictet . Memoires de la Societe de Physique et d'Histoire naturelle de Geneve, vol. xxxvii. Pp. iii 278+5 plates. (Geneve: George & Cie.; Paris: G. Fischbacher, 1012.)